Lesson 5 of 11 · 6 min
Aerobic respiration: pyruvate to acetyl CoA
NCERT §12.4
In the rice leaves above the water, oxygen is plentiful. There, pyruvic acid does not stop at the end of glycolysis: it crosses into the mitochondrion.
The lesson in notes
In short
Aerobic respiration completely oxidises organic substances in the presence of O₂, releasing CO₂, water and a large amount of energy. It is the most common type in higher organisms, and in eukaryotes it takes place inside mitochondria.
Pyruvate, the end product of glycolysis, is carried from the cytoplasm into the mitochondrion.
Two crucial events follow: all the hydrogen atoms are removed from pyruvate step by step, leaving three molecules of CO₂; and the electrons taken with those hydrogens are passed to O₂ while ATP is made.
The first event happens in the mitochondrial matrix; the second is located on the inner mitochondrial membrane.
In the matrix, pyruvate undergoes oxidative decarboxylation, catalysed by pyruvic dehydrogenase, which needs coenzymes such as NAD⁺ and coenzyme A: pyruvic acid + CoA + NAD⁺ → acetyl CoA + CO₂ + NADH + H⁺ (Mg²⁺ is needed).
One glucose gives two pyruvic acids, so this step makes 2 NADH and releases 2 CO₂ per glucose. The acetyl CoA then enters the tricarboxylic acid cycle.